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Contraction of blood vessels and observations on the circulation in the transparent chamber in the rabbit's ear.

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CONTRACTION O F BLOOD VESSELS AND OBSERVATIONS ON T H E CIRCTJLATION I N T H E
TRANSPARENT CHAMBER I N
THE RABBIT'S EAR
J . C. SANDISON
Laboratory of A n a t o m y , Y e d i c a l School, University of Pennsylvania,
Philadelphia, Pennsylvania
SEVEN FIGUR.EB
The contractility of small blood vessels is a subject which
has been studied in the living by a number of investigators
during the past sixty years. Before Stricker ('65) saw the
phenomenon of independent contraction of capillaries in the
nictitating membrane of the frog, these vessels were thought
to respond to circulatory changes in a passive manner only,
the flow of blood through them being regulated entirely by
the contraction and dilatation of vessels surrounded by muscle cells. Lister ('58) had noticed a dilatation of capillaries
in inflammation. The further studies of Golubew ('69),
Rouget ( '73), Tarchanoff ( '74), Roy and Brown ( '79), Steinach and Kahn ('03), and many others, established the fact
that capillaries are contractile as well as elastic. Most of
these observers studied the capillaries of amphibians and
obtained contractions by using mechanical, electrical, or
chemical stimuli.
Renewed interest in capillary contractility has recently
been aroused by the studies of Vimtrup ( '23)' working under
Krogh ( '22). Vimtrup made a careful study of the adventitial cells of capillaries which were first described by Rouget,
and which he termed 'Rouget' cells. Using the transparent
tails of living amblystoma larvae, he observed definite contraction of capillaries without any special stimulns, and
105
THE ANATOMICAL XEC'OXD, TOT.. 5 4 , N O . 2
106
J. C. SANDISON
described it as being inaugurated by the contraction of Rouget
cells. Parker ( ’ 2 3 ) and Federighi ( ’28) described, in certain
invertebrates, the active contraction of endothelium of capillaries on which no adventitial cells could be seen. E. R. and
E. L. Clark (’25), repeating Vimtrup’s studies on larvae of
Amblystoma and of Anurans, found active contraction of
capillary endothelium, but failed to corroborate Vimtrup as
regards thc part played by the ‘Rouget’ cells, since they
observed contraction of capillaries on which there were no
‘Rouget’ cells, and since, in capillaries on which sparsely
distributed ‘ Rouget ’ cells were present, the inauguration of
the contraction occtirred much more often away from the
‘Rouget’ cells than in their immediate neighborhood. Moreover, they noted that the endothelium contracted away from
the ‘Rouget’ cell, leaving a clear space between.
It is, then, clearly established that in Amphibia capillary
endothelium possesses the property of active contractility,
and that capillary contraction plays an important rale in regulating blood flow.
For the mammal, until recently, nothing has been definitely
known, in spite of a large number of studies by Hooker,
Krogh, Rich, Hill, Florey and Carleton, and others. The
reason for this uncertainty has been the unavailability of any
region in a mammal in which the smallest blood vessels could
be seen with sufficient clearness in the living under normal
conditions. This need has been supplied by the artificial production of a tissue so thin and transparent that the individual cells of the walls of arteries, veins, and capillaries
may be seen clearly with the highest microscopic lenses, and
in which prolonged studies may be made of the same vessel
similar to those carried out in the tail fins of amphibian larvae. The method developed in this laboratory, under the
direction of Dr. Eliot R. Clark, consists of the introduction
into a hole made in the ear of the rabbit of a thin, transparent, double-walled chamber with its sides open to the
deeper tissues of the ear, and into which new blood vessels
and connective tissue grow, forming a tissue which is per-
CONTRACTION OF BLOOD VESSELS
107
manent and which is essentially similar to the subcutaneous
tissue of the ear (Sandison, '24, '28 ; Clark, Kirby-Smith,
Rex, and Williams, '30). As described in a previous paper
(Sandison, 'as), the newly formed blood vessels undergo a
complete differentiation into arteries, arterioles, capillaries,
and veins. Recently (Clark et al., '31), a description has
been given of the ingrowth and differentiation of blood vessels in sixty standard chambers under controlled and approximately uniform conditions, with a correlated study of the
circulation, and the subsequent changes in the vascular
pattern over a period of months (over a year in several
cases).
The studies to be described here were made on chambers
constructed entirely of kodaloid (Sandison, '28). The vessels were all new ones which had formed by ingrowth into
the chamber from the subcutaneous vessels of the ear, and
the observations were carried out largely on a chamber in
which the vessels were from two to four and one-half months
old. The major purpose of the study was to find out, if possible, just what elements of the minute vessels are responsible
for the regulation of flow through the capillaries, whether
the capillary endothelium is contractile, what part the adventitial or 'Rouget' cells may play, to what extent the flow is
regulated by the smooth-muscle cells, and what other factors
may be concerned with the capillary circulation. It should
be mentioned that nerves were not seen in the present observations on the new vessels, and it was uncertain whether they
were present or not. However, important as this question
may be from many standpoints, it does not seriously affect
the primary object of this study. A preliminary account of
these observations was presented before the Physiological
Society of Philadelphia, May, 1928.
OBSERVATIONS ON CONTRACTION
It was early noted that, in a well-developed plexus, there
were frequent changes in the circulation; periods of active
flow alternating with periods of marked slowing or even of
108
J. C. SANDISON
actual stasis. Careful study showed that the circulation in
any given plexus of vessels changes in an almost rhythmical
manner.l On the average, about twice in each minute, the
free, active flow of blood is interrupted by a slowing or stasis
of a few seconds duration. Examination of the various parts
of the system to discover the factors responsible for this
periodic slowing brought out certain interesting facts. It
became clear that it is the contraction and relaxation of the
smooth-muscle cells of the arteries and arterioles which
cause the changes in the circulation. The adventitial or
'Rouget' cells, which are present in abundance on the precapillaries, play no part whatsoever in the contraction, and
the endothelium of the capillaries displays a power of contractility so slight that it is not a factor in the regulation of
the blood flow.
The contraction sometimes appears first in the main artery
of the ear, which narrows markedly, and may extend as a
wave along the arteries and their branches and the arterioles
until the last smooth-muscle cell is reached, three o r four
seconds being taken up ill the passage of the wave from large
artery t o small arteriole. The narrowing in the different
parts of the arteries may be partial or it may be sufficient to
block completely the flow of blood. Contractions of the
smooth-muscle cells around the arterioles do not occur simultaneously in all arterioles, and as a result of this alternating
contraction, the blood may flow first in one and then in the
opposite direction in the same vessel (fig. 1). The smoothmnscle cells on the larger arteries may remain contracted for
long periods of time under certain conditions, while the musClark and Clark ( '32) havr made observations on the liviiig preformed blood
vessels, using the 'preformed tissue' chamber (Clark et al., 'SO), in ' ~ ~ h i cthe
h
niain artery of the ear is retained and a thin, transparent area about 1.5 em. in
diameter, iiiclurling the preformed arteries, veins, and capillaries. Thcy dcscribc
the iiornial occurreiice of spontaneous rhythmic contractions of arteries, involving
the main artery of the ear, down t o smaller and smaller branches, and fiiid that
the different arteries and parts of the same artery each contract a t a different
tempo and t h a t the periodic contractions have a profound influence on the
distribution of blood t o different arras and on the direction of flow in different
vesvls.
CONTRACTION O F BLOOD VESSELS
109
cle cells on the arterioles rarely remain contracted f o r more
than a few seconds.
That it is the smooth-muscle cell which is almost exclusively responsible for the contraction of vessels comes out
most strikingly from a study of the smaller arterioles and
capillaries. In the arterioles the continuous sheet of smoothmuscle cells is succeeded by muscle cells in groups, and these
in turn by pairs, and finally by isolated single cells. They
can be readily seen, especially with the oil-immersion lens,
as small round structures outside of and encircling the endothelium. They can be distinguished easily from the adventitial cells which lie longitudinally along the vessel, and which
I
I
I
I
C
D
c
A
Fig. 1 Camera-lucida tracings, showing the size of the lumen of a n artery
(1) and its branch ( 2 ) , in CiEerent phases of dilatation and contraction. A,
both 1 and 2 dilated; B, 1 partially, 2 completely contracted; C, 1 completely,
2 partially contracted; D, both 1 and 2 completely contracted. x 310.
are larger in cross section. If such an area is watched it
will be seen that the arterioles contract at the places where
the smooth-muscle cells are present, and that the vessels
beyond the last cell narrow only to a very slight extent, if
at all.
It is most fascinating t o watch the contraction of a single
isolated smooth-muscle cell on an arteriole (fig. 2 ) . When
undergoing a contraction, it causes a rapid narrowing so that,
in the course of two o r three seconds, the lumen may be so
constricted that no blood cell can pass. It remains contracted
for three or four seconds and rather suddenly relaxes, the
relaxation being immediately followed by a rush of blood
through the vessel. It remains relaxed for periods of time
varying from ten seconds to a minute, and then contracts
110
J. C. SANDISON
again. The smooth-muscle cell does not always constrict the
lumen completely, for it may contract only partially and
narrow the lumen without obliterating it. The periods of
relaxation are definitely longer after the partial contraction.
While these definite contractions are occurring in the
smooth-muscle cells, which regulate the flow of blood, there
are only such general changes in the capillaries as can clearly
be explained on the basis of elasticity and of outside or inside
pressure. Following the shutting off of the blood flow, there
may be a slight general narrowing of the capillary, to be
followed by a slight widening when active circulat#ion is reI . I . ~ I I I . 1 ~ 1 1 . I . . . I . . . . I I . . . . . I . . . , . / . . . . . I I I I . . l . . . I . I . . . . . 1
9.08 A M .
9.09
9:11
9:lO
9:12
/
v
v
\
A
A
I . . . . I I . I . . I I . ~ . . . I . . . . . I . . . I . I . I . . . I . . . . I I . I . . . I I , . I . I . . . I . I
9:13
I . . . . .I
9 I8
9;14
.
I
.
.
.
1
.....I
919
9:15
. . . . . I . . . . .
9 20
9.16
I
9.17
. , . . , I . , , . . , . , . , -j
9 21
9 22
Fig. 2 Diagram showing the degree and rate of changes in caliber of an
artrriole following coiltraction of a single muscle cell which almost completely
surrounded the arteriole. The contraction periods of this cell occurred at the
same time as did the rhythmical ones of the arteries within the whole chamber.
sumed. Rut these changes are obviously secondary to the
contraction and relaxation of the smooth-muscle cell on the
arteriole. At times there has been observed a complete
emptying of an extensive capillary plexus, coincident with a
reduction in blood flow, and occurring simultaneously with
the contraction of the large supplying artery. This simulated
capillary contraction, but was found to be due to the pressure
exerted on the tissue by the thin, elastic celluloid cover of
the chamber, for pressure over the area with a fine glass rod
produced an identical picture. Evidently the widening of the
arteries raises the cover slightly, permitting easy circulation
through the capillaries, while the contraction of arteries
CONTRACTION O F BLOOD VESSELS
111
allows the cover to spring back and compress the capillaries,
particularly over the tables. This was further proved by
constructing chambers in which the covering celluloid was
cemented in places to the tables to make it rigid. In such
chambers the capillaries did not show this peculiar type of
emptying.
The circulation is markedly influenced by the development
of muscle cells on the newly formed capillaries as they become
transformed into arterioles. Changes in caliber were observed in the same vessels both before and after the appearance of muscle cells on their walls. It was found that before
the development of these cells the narrowing of such vessels
was always very slight, involved the whole vessel uniformly,
and followed the rhythmic contraction of the main artery just
described. After the appearance of muscle cells, however,
the same vessels were seen to display localized narrowings,
and such constrictions always occurred in the region of the
newly developed smooth-muscle cells.
OBSERVATIONS ON THE CIRCULATION
The manner in which blood flows through vessels and the
behavior of the blood cells in the normal blood stream were
observed and described many years ago by numerous investigators and only a few new observations have been made on
the circulation as studied in the rabbit's ear. However, since
most of the previous work on this subject has been carried out
on the mesentery of mammals where one is limited to short
observation periods, it is of interest to restudy the problem
in the transparent chamber, where the same blood vessels
may be seen from day to day for months, and the circulatory
changes in them observed during both their early formation
and their subsequent adult growth.
The different rates of flow in various kinds of vessels at
different stages of growth, together with the causes for these
variations, have already been discussed and partly analyzed
(Sandison, '28). One sees in the blood current in the rabbit's
ear the well-known axial stream of cells, and the compara-
112
J. 0. SANDISON
tively narrow, clear, plasma layer, or 'randzone,' which surrounds this rapidly moving central core. The throwing off
of the leukocytes into the peripheral layer and their slow
rolling motion along the vessel wall is also a phenomenon
which is readily seen.
I n this study it has been observed that the presence of the
clear peripheral stream is dependent upon the rate of flow:
it is widest when the blood is flowing rapidly, and occurs
chiefly in the arteries and arterioles, except when these vessels are so constricted that the single blood cells are squeezed
in passing through. When the circulation slows down or
stops, during a period of contraction of the arteries, this
peripheral layer is absent in all vessels. At such times the
erythrocytes and leukocytes are no longer limited to the axial
stream, but wander a t random; or they may settle to the
dependent part of the lumen, leaving only a clear layer of
plasma above. During a period of stasis, which may last for
several seconds or minutes, this sedimentation of blood cells
may be quite noticeable, particularly in the larger vessels.
Then, too, an uneven mixture of cells with plasma has been
observed during a period of sluggish or irregular flow of
blood through the capillaries-a condition which results in
part from an irregular contraction of first one arteriole and
then another. This independent contraction of arterioles
(i.e., one vessel closed at the same time another is open)
causes blood to be fed to the veins through the capillaries
and venules in the form of a broken stream. An uneven
mixture may also occur within an arteriole or an artery itself
as a result of contractions occurring at intervals along their
walls, leaving dilated portions of the vessel in which clumps
of cells collect (Art. G, fig. 5). When such contracted regions
again dilate and the circulation is resumed, the clumps of
cells pass on without mixing evenly again until they reach
the larger lumen of the venules. I n this connection the work
of Landis ('26) is of interest. He has been able to measure
capillary pressures during capillary stasis in the frog's
mesentery and to watch the flow of plasma through the endo-
CONTRACTION O F BLOOD VESSELS
113
thelium as indicated by the passage of injected dye. He finds
that wherever such a flow is present there is a considerable
change in the proportion of blood cells and plasma within the
lumen.
The phenomenon of ‘plasma skimming,’ a term introduced
by Krogh (?la), and that of leukocyte skimming may be
exhibited in various ways. The former is seen mainly in
partially contracted vessels or in capillaries which are cross
connections between the main path of the circulation and
which, even though dilated, have no circulation on account of
equal pressures at their two ends; it may be seen also in
blind-ending, new-growing tips. Not infrequently vessels
containing skimmed plasma, i.e., plasma without erythrocytes, are loaded with leukocytes which, along with the
plasma, have been skimmed off from the main circulation. In
fact, leukocyte skimming may be seen in practically any uncontracted vessel in which the circulation has temporarily
ceased, but which remains connected with other circulating
vessels .
The following observation on platelet skimming was also
made: in a single, very narrow capillary loop, whose two
ends were connected to a large circulating vessel, plasma
flowed at all times, as was indicated by the passing of the
smallest blood platelets. For many minutes only platelets
would pass. It was interesting to note that with an increase
of blood supply through the large vessel, erythrocytes would
be forced through the narrow loop. With a very rapid rate
in the larger vessel, accompanied supposedly by an increase
in blood pressure, even the largest leukocytes were forced
through the capillary, although its entrance was so constricted that the cells, in passing, were forced out into very
long and narrow forms.
Plasma skimming is not confined to capillaries, since it has
been seen in arterioles which are constricted almost completely at their proximal end and dilated along the remainder
of their course, the dilated portion containing only a single
blood cell here and there. Such plasma skimming in an arte-
114
J. C. SANDISON
riole is a rather complicated condition, and certain factors
must be present for its occurrence. I n the first place, the flow
of blood through any arteriole is dependent upon: the degree
of dilatation and the rate of blood flow in the artery which
supplies it, the pressures in the capillary bed which the arteriole itself supplies, the size of its entrance, and the caliber of
its entire lumen. Plasma alone will enter the arteriole when
its entire lumen or merely the lumen at its entrance, is constricted to a size much smaller than the blood cells, and when
the pressure of its arterial supply is not sufficient to force
cells through the constricted opening. When, as indicated by
the passage of platelets, plasma flows through a vessel under
these conditions, an occasional cell may enter it, but if both
the pressure in the capillary plexus beyond it and that at its
entrance become equalized (a condition which may result
from the passage of blood through another arteriole into the
same plexus of capillaries) blood flow will cease in this vessel,
the cells will be drawn off, and true plasma skimming will
usually follow. Krogh ( ’22), in studying the frog’s web and
tongue, saw a washing away of the erythrocytes, when he
stimulated a portion of a small artery branching from a
larger vessel almost to the point of complete contraction. He
stated that the current of blood through the small artery
seemed t o cease altogether, and that at the same time the
erythrocytes were washed out from the corresponding capillaries. I n the rabbit’s ear one also sees that the cells are
washed away from a capillary bed, following contraction of
the arterioles o r arteries, but there still may be a continuation
of the flow of the plasma containing platelets only.
In regard to the capillaries, however, this same plasma
skimming may occur as the result of another factor, i.e., the
reversal of flow in an arteriole-a phenomenon which occasionally takes place during a short period of stasis in the
artery. I n this case, the blood cells are drained out of the
capillary plexus in the absence of circulation. It will be
noted, therefore, that two types of plasma skimming have
been observed in the vessels of the rabbit’s ear, one in which
CONTRAOTION OF BLOOD VESSELS
115
the vessels contain a circulating plasma and the other in
which there is no circulation.
Venous and capillary pulsation have been seen in one
plexus or another at all times during the new growth of vessels, particularly in vessels which are either short circuits
between those which carry the main flow of blood, or blindending tubes. A very slight pulse is usually present in all
young capillaries, but it is barely perceptible to the eye except
when the rate of flow diminishes. I n the older tissue, however, a well-defined capillary pulsation is extremely rare,
except when the rate of flow is very rapid or very slow, and
even then it is present in only a few vessels. One small plexus
of blood vessels, containing a single pulsating capillary, was
studied carefully in order to determine the cause of this pulsation. The plexus contained two capillaries which emptied
close together into a very large vein, in which the flow was
even and constant. When the circulation throughout the
plexus became slow, one of these capillaries pulsated while
the other did not. It was seen that these two capillaries were
each supplied by a different arteriole, one of which supplied
several other capillaries with blood, while the second arteriole
had no other capillary branchings. I n the latter arteriole the
rate of flow was diminished, and it was in the capillary connected with it that the pulsation was observed. Blood cells
were seen to enter the large vein from this capillary in an
interrupted stream, a few cells with each beat of the heart.
The flow through the entire vein was perfectly stead-y and it
seemed probable that the pulsation in this particular case
was present in the one capillary on account of the short connection between the arteriole and vein, and absent in the
other on account of the greater number of capillaries which
its arteriole supplied.
As for the venous pulse, it may be due to a transmission
of the arterial pulse to the veins, or possibly to the contractions of the right auricle. It is difficult to explain the general
pulsation which may occur in veins and capillaries when the
circulation is extremely fast, as, for example, when the ear
116
J. C. SANDISON
is heated to 38°C. or above. At such a time the arterial wall
is distended slightly at each beat of the heart, the arterioles
are distinctly narrowed, the capillaries and venules are
slightly narrow, and the rate of blood flow in the large veins
is almost equal to that in the artery.
While the circulation in a capillary bed is almost entirely
regulated by the action of muscle cells on arterial vessels
supplying it, it has been found that the flow may be diminished or even stopped by a single leukocyte plugging a narrow
vessel. This occurs frequently, but is of minor importance,
since it is always temporary. One of the most favorable
places for such plugging is at the origin of the small arterioles
Cap
Artery
Fig. 3 Camera-lucida drawiiig of a precapillary braiich o f ail artery. The
artery has a double layer of muscle cells (Musc.) ; the entrance t o the preeapillarv
is almost obliterated by the bulging eiidothelial iiucleus (End.NucZ.) . hdveiititial
cell (Adv.) ; capillary (Cap.). X 412.
from their arteries. Normally, this region is constricted
partly on account of the bulging of endothelial cells into the
lumen. Such a bulging in a capillary is shown in figure 3.
At times the constriction is too great to permit the passage
of the leukocytes, though the more elastic erythrocytes map
pass quite readily. Unless the force of the blood stream
(always variable) is sufficient to push the obstructing cell
onward, the latter may stop the circulation in the capillaries
fed by the arteriole for varying lengths of time-sometimes
f o r several minutes. One such arteriole was watched and the
following was observed: With a rapid rate of flow, a condition which was always caused by a dilatation of the artery,
both the erythrocytes and the leukocytes were forced through
CONTRACTION OF BLOOD VESSELS
117
the narrow lumen in the form of an unbroken stream, even
though they were enormously distorted in passing. With a
moderate rate of flow the erythrocytes passed through easily,
though again distorted, but the leukocytes went through the
constriction in a jerking manner, apparently due to the effect
of the systolic waves upon them, and each one plugged the
vessel for a certain length of time. Occasionally the leukocytes' own ameboid activity would assist their passage. The
time required for the passage of a leukocyte through such a
constriction depended upon the activity (blood pressure) of
the general circulation, being greater with a feeble blood
stream. At periods of a steady, rapid rate of flow, the number of leukocytes which passed through this arteriole was an
average of forty per minute.
REACTION O F BLOOD VESSELS TO TEMPERATURE CHANGES
I n addition to the factors just described, which change the
rate of flow and the amount of blood distributed through the
vascular system, one other phenomenon has been studied in
this connection, namely, the reaction of vessels to temperature changes (figs. 4 and 5). The higher temperatures were
produced by an ordinary 60-watt electric-light bulb, the degree
of heat being regulated by the distance of the bulb from the
ear. The temperature was measured by placing a thermometer a few millimeters above that p a r t of the ear which
received the greatest amount of heat. The vessels were
studied a t three different temperatures: 37"C., 26" to 32"C.,
and 20°C. (produced by placing sponges dipped in ice water
directly 011 the surface of the chamber).
VCThile the heat was being applied, the circulation gradually
became more regular and faster, until, by the time the maximum of 37" was reached, it was quite regular in rate of flow
and the speed was exceedingly rapid, being almost as fast
in the veins as in the arteries. I n addition t o the rapidity of
flow, a general pulsation of the vessels could be seen. The
rhythmical contractions previously described now occurred
only at very long intervals and lasted for a very brief period
118
J. 0. SANDISON
of time. After the light bulb was removed and as soon as the
ear became accustomed once more to room temperature, the
circulation continued as it did previous t o the experiment.
The sticking of leukocytes to the walls of capillaries and their
emigration through the vessel walls, following heating of the
ear to 37 C., has already been described ( Sandison, '31).
When the ice packs were applied, the branches of the larger
arteries contracted completely, and all circulation in the
chamber stopped. Very occasionally the arteries would open
slightly and permit a sluggish flow of blood, but this partial
dilatation had very little eEect upon the capillary circulation.
The exact point on the arteries where this marked contraction
ended varied in all of them, but it rarely extended to the
arterioles, most of which were slightly dilated. When the
ear was brought back to room temperature, the circulation
again returned to its normal condition.
The specific reaction of the different types of vessels during these experiments may be followed in figures 4 and 5.
Here it is seen that the main vessels concerned in the regulation of the blood flow are the artery and arteriole. At 20°C.,
the artery, by its contraction, is alone responsible for the
stasis which develops, the arterioles are incompletely dilated
in the region of their muscle cells, while all other vessels are
wider than at any other temperature. The rhythmic contraction of the arteriole disappears. The small vessels at
32°C. are on the whole narrower than at 20°C., and the
rhythmic contraction of the arterial vessels is more regular
at this temperature. At 37"C., the capillaries, the arterioles,
and the arteries are smaller than at any other temperature;
the veins, though larger than at 32"C., are smaller than
at 20°C.
O
Fig. 4 Camera-lucida drawings, showing changes in the caliber of all types
of vessels with three different degrees of temperature. The insert a t the upper
right corner shows the parts of the plexus from which the segments of different
vessels shown in figures 4 and 5 were taken. A , arteriole; ( H , origin of arteriole
A ) ; B, a precapillary; C, a loop of the prepostcapillary; D , a venule; Dil., greatest degree of dilatation ; Con., greatest degree of coiltraction ; N o Con., n o contraction; a and a l , flame group of muscle cells; b and b l , the same adventitial
cell. X 310.
119
:ONTRACTION OF BLOOD VESSELS
Dil.
1
Con.
D i I.
c
e7
Con.
1
B
Arteriole
D i I.
hrtrriolr
cap
I'reenp
32T.
No
Con.
/ A
f 0
A
B
20°C.
Figure 1
c
D
120
J. C . SANDISON
REACTION O F T H E BLOOD VESSELS TO ADRENALINE AND
HISTAMINE
For these experiments a preparation was used containing
adrenaline, 9/20 grain ; chloretone, 24 grains, and physiological salt solution, 1 fluid ounce. For intravenous injection a
dilution of 1: 100,000 was employed. Observations of the
blood vessels in the transparent chamber were made during
the injection of the drug into a vein of the opposite ear, and
a region among these vessels was selected where an artery
of a caliber of over 125 v, with its arterioles, capillaries,
venules, and veins could be watched. This artery had at
least three layers of muscle cells around it. Before the injec-
Art
E
Vein
F
Fig. 5 Camera-lucitla sketch, showing changes in calibcr a t diff ereiit tempcratures of three other vessels of the same plexus shown i n the inset figure 4. E , a n
artery having two layers of muscle; P’, a vein; G , the more proximal portion of
the artery; E, point beyond whieli coiitraetioii did iiot occur at 2 0 ”. x 206.
tion was begun, the normal changes in caliber of this vessel
and of its arteriole branchings mere noted, and they coiiformed to the changes whicli hare been previously described.
At no time did this artery constrict more than one-half of
its fully dilated caliber and the rhytlim of its contraction was
similar to that which has also been previously described for
arteries in this chamber. Surrounding the wall of the proximal half of the visible portion of this large artery were numerous macrophages which contained a dark yellow-brown
pigment. The vessel had slight local contractions here and
there along its wall.
The injection needle was quickly thrust into the vein with
one movement. Almost immediately the arterial vessels com
CONTRACTION O F BLOOD VESSELS
121
stricted slightly more than normal, and in a few seconds they
dilated fully. This is the usual response to any disturbance
to the animal. Then, after one minute, a t the end of which
time these vessels were still dilated, a slow injection of the
adrenaline was begun. The large artery began constricting
one and one-half minutes after 0.3 cc. of the 1:100,000 solution had entered the vein. Injection was then stopped. A
few seconds later the large artery constricted to about 25 p
in caliber (one-sixth its dilated caliber) along its proximal
half. The degree of constriction was less along the remainder of its course, being less marked the more peripherally
one followed it. The normal, locally contracted regions were
the points of greatest constriction in any one segment of the
vessel. The lumen, even though greatly constricted by contraction of the muscle cells which were much thicker than
normal, widened slightly with each beat of the heart.
The arterioles were greatly constricted along most of their
course, but they showed only a partial contraction near their
capillary terminations, even though they were surrounded
in that region by a single layer of muscle cells (fig. 6). They
were most constricted a t the point where they took origin
from the large artery-a point where they are normally narrower (fig. 3 ) . The venules also narrowed, but to a slight
extent only. The capillaries were apparently unaffected,
except for the usual very slight changes which normally accompany changes in blood pressure, i.e., a slight dilatation
with decreased rate of blood flow. The flow of blood in the
capillary bed varied in different capillaries from a complete
stop to a moderate rate, depending upon their proximity to
an arteriole. In most of the main pathways which lie between
the arteriole and the venule a slow circulation prevailed.
One interesting observation during the contraction of the
large artery was the effect upon the pigmented macrophages
which surrounded a part of this vessel. They were apparently unchanged in regard to their position-a
wide clear
space between them and the muscle cells of the vessel wall
being quite evident, whereas previous to the time of injection
they had lain directly upon these muscle cells.
THE A N A T O M I C A L RECORD, VOL. 54, N O .
1
122
J. C. SANDISON
The constriction period in all vessels was not over two
minutes, and one and two-thirds minutes after the injection
was stopped the arterial vessels began to dilate; twenty seconds later, the dilatation was almost complete. At this
moment a second injection was begun, the needle having been
kept in place, and 1.2 cc. of the adrenaline solution was
steadily emptied into the vein over a period of four minutes.
NC
t
Fig. 6 Camera-lucida drawing, showiiig effect of ail iutraveiious injectioii of
adreiialiiie chloride (1: 100,000). The arteriole contracts, while the capillaries
aiid veiiules are uiiaff ected. Dotted line indicates degree and limit of contraction.
Eiidothelial nuclei dotted, adventitial cells cross-hatched, smooth-muscle clear
ovals. N.C., 110 coiitractioii beyond this point. X 316.
One and one-half minutes from the beginning of this second
injection, after 0.3 cc. had again entered the circulation, there
was a repetition of the change in caliber of the vessels similar
to that noted after the first injection. At the end of two
minutes, dilatation was not complete, but there was a considerable widening of the arterial vessels. The injection was
continued, and one-half minute following this incomplete dilatation a constriction of the vessels again occurred, but to a
much less degree than the one which just preceded it. The
CONTRACTION O F BLOOD VESSELS
123
vessels remained in this state of partial constriction for one
and one-half minutes after the injection, at which time they
dilated and this dilatation, which was general, lasted a t least
one-half hour. The effect of this arterial dilatation on the
capillary circulation was marked and brought about a great
increase in the rate and amount of flow through all vessels
with the establishment of circulation in capillaries which were
previously open but non-circulating.
Under the action of a more dilute solution of adrenaline
(0.3 cc. of 1: 500,000) the capillaries gave the same response,
but there was less of the primary slowing of the capillary
circulation, partly on account of a lesser contraction of the
arterial vessels. When 2 minims of 1: 1000 solution were
injected subcutaneously, the vessels responded as they did
with the intravenous injection, except that the contraction of
arteries and arterioles was prolonged for seven minutes o r
more, and the return of the normal rhythm of these vessels
appeared much later. Local application gives such a picture
as shown in figure 7.
The effect of histamine upon the blood vessels was also
observed. The same method of study as that used with
adrenaline was employed, except that only one dilution
(1:100,000) was used, and only the intravenous route of
injection was chosen. The action of 0.004 mg. of this drug
resulted in dilatation of arterioles and arteries with almost
complete stasis throughout the vessels of the chamber for
over two hours. The greatest degree of dilatation occurred
in the arterioles, since they widened to twice their usual
diameter. The capillaries were unchanged in caliber, except
for the usual slight dilatation following lack of flow through
them, and all of the previously non-circulating, wide-open
capillaries were filled almost to capacity with blood in stasis.
The very narrow capillaries, which are the retracting or the
new-growing vessels, were observed particularly for dilatation, but they also were unchanged. Frequent reversals of
flow in all vessels were noticed. The next day, eighteen hours
later, cc. of adrenaline was administered subcutaneously in
+
124
J.
C. SANDISON
the abdominal region, and all of the arterial vessels, which
had dilated with the injection of histamine, then contracted.
The results, therefore, of the action of these two drugs on
the vessels of the rabbit’s ear show that the various responses
are chiefly confined to the vessels which are surrounded with
muscle cells. With dilute intraveous injections, adrenaline
causes a fleeting constriction of all arterial vessels in the
Capillaries
Arteriole
1
2
Fig. 7 Camera-lucida drawing, showing degree and limit of actioii of a local
iiijectioii of 1: 1000 adreiialiiie chloride. M , muscle cell. 1, preceding, aiid
2, folIowiiig injection. X 310.
chamber with diminished capillary circulation, which action
is quickly followed by an arterial dilatation, accompanied by
a much more rapid capillary flow than that usually present in
the normal circulation. Histamine causes a still greater diminution of the capillary circulation, and dilatation of all the
peripheral arteries and arterioles with the strength of solution used. Neither drug acts, apparently, on naked
endothelium.
CONTRACTION O F BLOOD VESSELS
125
SUMMARY
hlicroscopic observations have been made on new blood
vessels which have grown into a transparent chamber introduced into the rabbit’s ear, and which have persisted for
from two to four and one-half months, with the following
results :
The local control of blood flow in this newly formed tissue
appears to reside in the smooth-muscle cell on the arteriole.
Adventitial (‘ Rouget ’) cells are present in large numbers,
but do not appear to contract.
Capillaries proper, with or without perithelial (‘Rouget ’)
cells, have such a limited power of contractility that they
seem to play no significant part in the control of circulation.
While their caliber manifests changes, the changes seem t o
be passive rather than active, and brought about chiefly by
changes in pressure both within and without, coupled with a
certain degree of elasticity of endothelium. However, in the
persistent absence of blood flow through a capillary it may
gradually narrow until its lumen may permanently disappear
-rather a retrogression in growth than contraction.
Nothing was seen which could be interpreted as active contraction of any of the veins or venules under observation.
Application of heat to the ear caused an extremely rapid
flow of blood, the arteries, veins, and capillaries maintaining
a uniform caliber. Cold applications caused persistent contraction of larger arteries with sluggish flow and slight widening of small arterioles, capillaries, and veins. With both
heat and cold there was a marked degree of sticking of leukocytes to the walls of veins and venous capillaries, and, in the
case of heat, extensive emigration of leukocytes through the
endothelial wall.
Injection of adrenaline was followed by marked contraction
of the arteries and arterioles at places where they were obviously provided with smooth-muscle cells, while capillaries and
venules showed only slight, and apparently passive, changes
in caliber. Contraction of arterioles was followed, after a
few minutes, by a half-hour’s dilatation.
126
J. C. SANDISON
Intravenous injection of histamine produced relaxation and
widening of the small arteries and arterioles, coupled with
diminution in blood flow. Capillaries and small veins showed
no appreciable change in caliber.
Many of the interesting pictures to be seen in watching the
circulation are described, most interesting of which are perhaps ‘plasma skimming’ (Krogh), platelet ‘ skimming, ’ and
leukocyte ‘skimming. ’
Whether the new vessels under observation were supplied
with nerves was not determined.
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CONTRACTION O F BLOOD VESSELS
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